Sichuan Kelun-Biotech Biopharmaceutical Co., Ltd. ("Kelun-Biotech" or the "Company", 6990.HK) announced that the Independent Data Monitoring Committee (IDMC) concluded that the Phase III clinical study (OptiTROP-Breast03) of the Company's trophoblast cell-surface antigen 2 (TROP2)-directed antibody drug conjugate (ADC) sacituzumab tirumotecan (sac-TMT, also known as SKB264/MK-2870)(佳泰莱^®) versus investigator's choice of chemotherapy as first‑line treatment for unresectable locally recurrent or metastatic triple‑negative breast cancer (TNBC) has met its primary endpoint of progression‑free survival (PFS) at a prespecified interim analysis, demonstrating a statistically significant and clinically meaningful improvement. Overall survival (OS) data are immature, a positive trend is currently observed.

OptiTROP-Breast03 is a randomized, open‑label, multicenter Phase III clinical study designed to evaluate the efficacy and safety of sac‑TMT versus investigator's choice of chemotherapy in patients with unresectable recurrent or metastatic TNBC who have not received prior systemic therapy for advanced disease. The enrolled population includes patients with programmed death ligand 1 (PD-L1)‑negative expression, as well as those with PD‑L1‑positive expression who have relapsed after prior anti-PD-(L)1 inhibitor in early stage disease. Two independent primary endpoints of the study are PFS and OS. At this pre-specified interim analysis, sac-TMT monotherapy demonstrated a statistically significant and clinically meaningful improvement in PFS. OS data are immature, a positive trend is currently observed. Follow-up will continue per protocol and further evaluation will be conducted in subsequent prespecified analyses. The safety profile of sac-TMT was consistent with that observed in previously reported studies, and no new safety signals were observed. Based on the results from the interim analysis, the Company plans to communicate with the Center for Drug Evaluation (CDE) of the National Medical Products Administration of China regarding the subsequent regulatory pathway for sac‑TMT in this indication.

This is the first registrational Phase III clinical study of sac-TMT to achieve positive results in the first-line treatment of TNBC.Previously, sac-TMT has been approved for the treatment of unresectable locally advanced or metastatic TNBC in patients who have received at least two prior systemic therapies (including at least one for advanced or metastatic disease) based on the results of OptiTROP-Breast01 study. The achievement of the primary endpoint of PFS in the Phase III OptiTROP-Breast03 study builds on the ongoing development of sac-TMT and supports further evaluation of its potential in the first-line setting in TNBC and across treatment settings, aligned with the Company's broader clinical development strategy to address patient needs.

Currently, the global Phase III TroFuse-011 study (NCT06841354) of sac-TMT monotherapy or in combination with pembrolizumab as first-line treatment for PD-L1 Combined Positive Score (CPS)＜10 TNBC is ongoing.